Activating the lattice oxygen oxidation mechanism in amorphous molybdenum cobalt oxide nanosheets for water oxidation

The cost-effective deployment of several key energy technologies, such as water electrolysis, CO2 electroreduction and metal-air batteries, relies on the design and engineering of cost-effective catalysts able to accelerate the...

Characteristics of Low-Oxygen Oxidation Ditch with Improved Nitrogen Removal

This article presents a study on the operational stability of laboratory oxidation ditches, designated for synthetic and real wastewater and operable at low concentrations of dissolved oxygen. The project encompassed the stability monitoring of activated sludge depending on sedimentation characteristics and hydrobiological indicator microorganisms, determining (1) the size of sludge floccules and (2) the main functional groups of microorganisms identified in the course of the PCR analysis and reaction rates, plotted using the Michaelis–Menten enzymatic kinetics for the mixed culture biomass. The most stable system involves a bioreactor featuring dissolved oxygen gradients that range from 1.9 to 0.15 mg/L s, a specific organic load of 0.21 gBOD/g/d and a hydraulic retention time of 12 h. A built-in settling tank allows the consideration of the potential generation of large floccules of activated sludge in oxidation ditches (at least 300 μm) that increase the efficiency of simultaneous nitrification and denitrification. Thus, the obtained reaction rates can be used in calculations and simulations of the operation of oxidation ditches at low concentrations of dissolved oxygen.

Strengthened Oxygen Oxidation of Ferrous Ions by A Homemade Venturi Jet Microbubble Generator towards Iron Removal in Hydrometallurgy

Iron normally exists in the form of ferrous ion (Fe2+) in primary ore deposits of valuable metals. To remove iron from hydrometallurgical leaching solution or suspension by precipitation, ferrous ion should be oxidized to ferric ion (Fe3+) first. Due to the low oxidation rate of Fe2+ by the traditional oxygen oxidation method, industry has to use more agitating barrels, steam, and compressed gas, as well as a larger workshop area, which dramatically increases the equipment investment and operation costs. In this study, a strengthened oxygen oxidation method for Fe2+ using a homemade venturi jet microbubble generator is proposed. Microbubbles of air, oxygen, or oxygen-enriched air can be formed in the leaching solution or suspension, which can greatly improve the dissolved oxygen content in the solution and increase the gas-liquid contact area, thereby accelerating the oxygen oxidation rate of Fe2+ to Fe3+ and realizing the rapid iron removal of the leaching solution or suspension. By measuring the residual concentration of Fe2+ in the solution after oxidation reaction, it was found that the pump power, solution temperature, pH, concentration of Cu2+, and solution flow rate had great effects on the oxidation performance of the produced microbubble. By analyzing the images of the microbubbles and measuring the dissolved oxygen content in the solution, it is confirmed that the accelerated oxidation reaction rate of Fe2+ using the new proposed method was mainly due to the increase of the dissolved oxygen amount in the solution. Moreover, this method can significantly increase the purification depth of iron ion, expand production capacity, and decrease energy consumption.

The removal of turbidity and toxic metals in the AMD using a combination of saw dust, bentonite clay and synthetic CaMg.2(OH)2

Sets of experiments were conducted using 200 mL of synthetic acid mine drainage(AMD) into five 500 mL glass beaker, dosed with varying quantities of bentonite clay, saw dust and CaMg.2(OH)2 respectively and as a flocculent (bentonite clay, saw dust and CaMg.2(OH)2), mixed at 250 and 100 rpm for 2 and 10 mns respectively. The samples settled for 1 hour after which the pH, conductivity, turbidity, dissolved oxygen, oxidation reduction potential and toxic metals were measured. The turbidity removal of treated AMD samples treated with a flocculent (0–23 NTU) is lower compared to that of the samples treated with bentonite clay and saw dust (27–32 NTU). Results show 100% removal of Ni, moderate percentage removal of Fe and slightly lower percentage of Cu in treated AMD using a flocculent. Turbidity removal in treated AMD using a flocculent is higher compared to that of the samples treated with bentonite clay, saw dust or CaMg.2(OH)2. Treated AMD using flocculent has low Ca, Mg, Cl− and SO42− content (>84.8%). The SEM micrograph of the sludge of the sample with a combination of 1.5 bentonite clay, 1.5 g saw dust and 20 mL 0.025 M CaMg.2(OH)2 dosage shows optimal sorption of turbid materials.

Unraveling the role of oxygen vacancy in the electrooxidation of 5-hydroxymethyfurfural on Co3O4

The electrooxidation of 5-hydroxymethylfurfural (HMF) offers a promising green route to attain high-value chemicals from biomass. The HMF electrooxidation reaction (HMFOR) is a complicated process involving the combined adsorption and coupling of organic molecules and OH- on the electrode surface. An in-depth understanding of these cooperative adsorption behaviors and reaction processes is fundamentally essential. Herein, the adsorption behavior of HMF and OH-, and the role of oxygen vacancy on Co3O4 are initially unraveled. Correspondingly, instead of the competitive adsorption of OH- and HMF on the metal sites, it is observed that the OH- could fill into oxygen vacancy (Vo) before couple with organic molecules through the lattice oxygen oxidation reaction process, which could accelerate the rate-determining step of the dehydrogenation of 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) and enhance the overall conversion of HMF on Vo-Co3O4. This work sheds a depth insight on the catalytic mechanism of oxygen vacancy, which benefits designing a novel strategy to modulate the multi-molecules combined adsorption behaviors.

Synthesis of Cardiotonic Steroids Oleandrigenin and Rhodexin B

This article describes a concise synthesis of cardiotonic steroids oleandrigenin (7) and its subsequent elaboration into the natural product rhodexin B (2) from the readily available intermediate (8) that could be derived from the commercially available steroids testosterone or DHEA via 3 step sequences. These studies feature an expedient installation of the β16-oxidation based on β14-hydroxyl directed epoxidation and subsequent epoxide rearrangement. The following singlet oxygen oxidation of the C17 furan moiety provides access to oleandrigenin (7) in 12 steps (LLS) and 3.9% overall yield from 8. The synthetic oleandrigenin (7) was successfully glycosylated with L-rhamnopyranoside-based donor using Pd(II)-catalyst, and the subsequent deprotection under acidic conditions provided cytotoxic natural product rhodexin B (2) in 68% yield (2 steps). <br>

Synthesis of Cardiotonic Steroids Oleandrigenin and Rhodexin B

This article describes a concise synthesis of cardiotonic steroids oleandrigenin (7) and its subsequent elaboration into the natural product rhodexin B (2) from the readily available intermediate (8) that could be derived from the commercially available steroids testosterone or DHEA via 3 step sequences. These studies feature an expedient installation of the β16-oxidation based on β14-hydroxyl directed epoxidation and subsequent epoxide rearrangement. The following singlet oxygen oxidation of the C17 furan moiety provides access to oleandrigenin (7) in 12 steps (LLS) and 3.9% overall yield from 8. The synthetic oleandrigenin (7) was successfully glycosylated with L-rhamnopyranoside-based donor using Pd(II)-catalyst, and the subsequent deprotection under acidic conditions provided cytotoxic natural product rhodexin B (2) in 68% yield (2 steps). <br>